Nuclear magnetic resonance

Nuclear magnetic resonance is the interaction of atomic nuclei with radiofrequency fields in a magnetic field. It underlies methods for measuring molecular structure, chemical environments, and internal images.

Nuclear spin: An intrinsic quantum property of an atomic nucleus that gives it angular momentum and a magnetic moment. Nuclear magnetic resonance depends on spin-bearing nuclei behaving as tiny magnetic moments.
Nuclear magnetic resonance spectroscopy: A technique that uses nuclear magnetic resonance signals to determine molecular structure and chemical environments. It uses resonance frequencies and couplings to distinguish atoms within molecules.
Isidor Rabi: A physicist who developed molecular-beam magnetic resonance methods and received the 1944 Nobel Prize in Physics. His experiments established magnetic resonance as a precise probe of atomic and nuclear properties.
Magnetic moment: A measure of the strength and orientation of a system's magnetic influence. A nucleus produces an NMR response only when it has a magnetic moment.
Electron paramagnetic resonance: A spectroscopic technique that detects transitions of unpaired electron spins in magnetic fields. It probes electron spins rather than the nuclear spins measured by NMR.
Larmor precession: The precession of a magnetic moment around an applied magnetic field at a frequency proportional to field strength. It sets the resonance frequency that radiofrequency excitation must match.
Magnetic resonance imaging: A medical imaging technique that uses nuclear magnetic resonance signals and magnetic-field gradients to form images. It encodes spatial position into NMR signals to map tissues noninvasively.
Felix Bloch: A physicist who independently demonstrated nuclear magnetic resonance in bulk matter in 1946. His induction method made nuclear resonance observable in liquids and solids.
Nuclear magnetic moment: The magnetic dipole moment associated with a nucleus's spin and internal structure. Its size determines how strongly a nucleus interacts with fields and radiofrequency energy.
Optical spectroscopy: Methods that measure how matter interacts with ultraviolet, visible, or infrared light. Its transitions typically involve electronic or vibrational energies, not nuclear spin states.

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